In the field of closures, including doors, window sashes, patio doors and the like, many developments have taken place in regards to items such as the doors, the glazing units, hardware and the like, while the associated frame units have remained substantially unchanged. This has presented both thermal and structural problems, as well as aesthetic problems.
In light of the present invention it is now apparent that many of these problems may have stemmed from the continued use of pre-existing types of closure frame structures, in regards both to their use as movable closure frames, and as the peripheral or semi-peripheral support frames therefor.